1. Field of the Invention
This invention relates to an image processing apparatus, and more particularly, to an image processing apparatus which includes a printer unit capable of providing, for example, a full-color output.
2. Description of the Prior Art
Heretofore, when a hard copy of the picture surface of an engineering work station (hereinafter termed an EWS) is output from a printer, the display color of the printer has been limited by the number of display gradations (the number of planes) on a bit-map display (hereinafter termed a display device) of the EWS.
A case will now be considered wherein the printer has a full-color (8 bits for each of R (red), G (green) and B (blue) signals) output function, and the number of display gradations of the display device is 8 bits (256 gradations). The EWS usually includes a multiwindow system, and various kinds of applications are simultaneously displayed in the form of a plurality of windows on the picture surface. In such an EWS, even if an application logically has a function of displaying a full-color image, it is impossible to display an image with the original number of gradations due to a limitation of the hardware of the EWS display device. Hence, the image is displayed as a window on the display device after performing depth reduction of the original image so that the number of gradations is equal to or less than 286 using a depth reduction method, such as a dither method or the like. If a hard copy of the picture surface is subsequently output from the printer, the portion of the window which must have originally been subjected to full-color display is a bit-compressed output.
If it is desired to print an image with an original number of gradations, that is, as a full-color image, the full-color image must be printed separately from the hard copy of the picture surface. Alternatively, the image must be output with the number of gradations of the EWS in the form of the hard copy of the picture surface together with applications other than the image displayed on the display device.
In the above-described conventional approach, however, in order to obtain a hard copy of an image with an original number of gradations of the image while preserving both the window of the image displayed in a compressed form and windows of applications other than the full-color image, it is necessary to temporarily receive hard-copy data of the picture surface and data of the full-color image in buffer regions and explicitly synthesize these data. This is a complicated operation for the operator.